1. Field of the Invention
The invention relates to array microphones, and more particularly to beamforming.
2. Description of the Related Art
A microphone system with beamforming capability comprises an array microphone and a beamforming module. An array microphone comprises a plurality of microphones. When the array microphone is used to receive a sound from a target object, the microphones of the array microphone convert the sound into a plurality of raw audio signals with slight phase differences therebetween. The beamforming module then performs a beamforming process according to the phase differences of the raw audio signals to generate a processed audio signal comprising sound components coming from a direction of the target object. The processed audio signal therefore comprises more sound components of the target object than the raw audio signals, and a quality of the processed audio signal subsequent to the beamforming process is therefore higher than those of the raw audio signals.
When a beamforming process is performed, the beamforming module must first determine a direction and a receiving range of sounds of the target object, and then filter out noises coming from directions outside of the receiving range to obtain the processed audio signal. To determine the receiving range of sounds of the target object, the beamforming module must perform a plurality of complicated frequency-domain analyses on the raw audio signals generated by the array microphone. The determined receiving range, however, may be inaccurate, thus, erroneously filtering out a portion of sound components of the target object from the raw audio signals and degrading performance of the microphone system. To improve performance of the microphone system, extra auxiliary information for determining a receiving range of a beamforming process is therefore required.
An electronic apparatus, such as a notebook, a cell phone and digital camera, often comprises both a microphone system receiving sounds and a camera system capturing images. When the camera system captures images of a target object, a camera of the camera system must be aimed at the target object for shooting images of the target objects. To obtain an image with a proper covering range of the target object, a focal length of the camera must be properly adjusted. When the camera captures an image of multiple target objects, the camera system performs a face detection process to determine a number of the objects. All of the aforementioned information including the shooting direction, the focal length, and the object number can be used to define the receiving range of a beamforming process of the microphone system. Thus, a method for receiving sounds with auxiliary information from a camera system is provided.